This invention relates to gas-liquid contact apparatus, and it particularly pertains to the structure and manufacture of the parts that distribute liquid onto a bed of packing media.
In a typical gas-liquid contact apparatus, packing media is contained in a sealed, vertically elongated vessel frequently referred to in the industry as a column or tower. Packings may be structured packings such as corrugated sheets of screen or sheet metal, or random particles such as rings or saddles types, all of which are well known in the art. Liquid is usually distributed on the upper surface of the packing media by an orifice pan, trough or spray nozzle distributor. Gas is introduced to the vessel through a gas inlet nozzle, flows through the packing media where it contacts the liquid on the packing media surfaces, and then exits through a gas outlet nozzle in the vessel. As the liquid moves downwardly through the packing media under the influence of gravitational forces, it wets the surface of the packing media, forming a renewing liquid surface to promote the effective contact between the fluids. After the liquid passes through the packing, it flows to a liquid outlet means. Normally, the gas flows countercurrent to the liquid flow, but cocurrent arrangements are sometimes used.
The present invention is directed to improvements in a type of distributor shown in Robbins' U.S. Pat. No. 4,472,325, assigned on its face to The Dow Chemical Company. In this known apparatus, liquid flows onto the packing media from vertical seamless tubes which are mounted on liquid-receiving pans. These tubes protrude above and below the decks of their respectively pans, and their upper portions have vertical slots milled therein to meter the flow of liquid into the tubes. These tubes are precisely welded into elevated positions.
According to current practices, the manufacture of flow tube type distributors is a costly and labor intensive task, requiring each tube to be precisely cut, slotted, and welded to the deck. Unless extreme care is taken, there will be maldistribution of the liquid due to unequal slot sizes, unequal slot elevations, and unequal elevations of the upper edges of the tubes. Maintenance is expensive because, when flow tube replacement is required, the entire distributor must be removed from the column and replaced.
An objective of the invention is to provide a distributor which uniformly distributes liquid to the packing media in the vessel throughout a wide range of liquid flow including very low rates.
Another object is to provide a manufacturing method which is simple, relatively inexpensive, and is capable of producing distributors of varying dimensions from a wide variety of materials.
A further object is to provide a distributor which, relative to existing distributors of this type, is less expensive to manufacture and provides more uniform liquid distribution.
Still another object is to provide a distributor in which fouled or corroded flow tubes are field replaceable in the respect that they can be removed and replaced in the field, without removing the deck from its column supports.